－May I smoke here?

－If you ________, choose a seat in the smoking section．

A．should

B．could

C．may

D．must

Although the causes of cancer ________, we do not yet have any practical way to prevent it．

A．are being uncovered

B．have been uncovering

C．are uncovering

D．have uncovered

You ________ me up．I don't have to go to work today．

A．can't have woken

B．didn't wake

C．needn't to wake

D．needn't have woken

－Do you still remember the day when we want to the Great Wall?

－I can't remember it well, but ________ sometime last autumn?

A．might it be

B．could it have been

C．could it be

D．must it have been

－Don't be so anxious about that．Helen ________ a note．

A．may leave

B．should leave

C．might have left

D．can have left

－The woman biologist stayed in Africa studying wild animals for 13 years before she returned．

－Oh, dear! She ________ a lot of difficulties．

A．may go through

B．might go through

C．ought to have gone through

D．must have gone through

I wonder how he ________ that to the teacher．

A．dare to say

B．dare saying

C．not dare say

D．dared say

－Lucy doesn't mind leading you her dictionary．

－She ________．I've already borrowed one．

A．can't

B．mustn't

C．needn't

D．shouldn't

John, look at the time．________ you play the piano at such a late time?

A．Must

B．Can

C．May

D．Need

－Who is the girl standing over there?

－Well, if you ________ know, her name is Mabel．

A．may

B．can

C．must

D．shall